If the age of the edifice is confirmed, the discovery could push back the age of Tlatelolco—as well as that of its nearby "twin city" Tenochtitlán—by a century or more, said Salvador Guilliem of Mexico's National Institute of Anthropology and History.

Guilliem, who is leading an archaeological effort to study Tlatelolco, said the structure's construction suggests it could have been built as early as A.D. 1100 or 1200, at least a century earlier than historical accounts suggest the city was founded.

While Guilliem's team continues to work on determining the new pyramid's age, the researchers have already uncovered new insights into the Grand Temple.